Harvest months could see heavier-than-normal tropical storm season

BATON ROUGE, La. – The growing season’s bookends are dry but farmer diaries they hold spill water when opened. Rain day notations abound.

“In March, we had less than half the normal amount of rain,” says Barry Keim, Louisiana state climatologist. “April had a normal amount of rain. May, though, started a trend of rainy weeks. And the word ‘rainy’ probably doesn’t do that period justice.”

Louisiana averaged 9.5 inches of rain in May – almost twice the norm. A swath running from Baton Rouge to Lake Charles – right along the I-10 corridor – “really got hammered,” says Keim. Much of that area received 20 inches of rain or more -- most falling in an eight-day period.

“Driving that was an upper air disturbance that hung over the state producing copious rain. As soon as that disturbance moved out, a surface cold front rushed in bringing even more rain.”

Louisiana dried out towards the end of May and then June arrived. Keim, who works at the Southern Regional Climate Center in Baton Rouge, describes June as an “incredible month” for much of the Delta and Texas. Mississippi had its wettest June on record. Louisiana (which averaged 11.5 inches – 6.5 inches over the norm) and Texas ended up with their third wettest June.

Keim says what’s interesting is the June rains weren’t driven by a single, major storm. “We just had repeated thunderstorms. There were several late-season fronts that penetrated the area, which is rather unusual for that time of year. There were also a number of upper air disturbances that rippled through and kept the storms firing off.”

Some areas had “incredible” June runs: Alexandria had 25 days of rain as did a New Orleans site. Several areas around the state had 23 rain days.

Normally by June Louisiana has settled into a summertime weather pattern. “That’s where afternoon convective showers slide though. You can set your watch by these things – they’ll show between lunch and mid-afternoon. This June, though, the storms were coming through at all times of night and day. That’s very unusual.”

The two wettest Junes on record in Louisiana occurred in 1989 and 2001. Both were driven by single events, both tropical storms named Alison.

Since this June’s rain wasn’t caused by a single event, “the million dollar question is what this portends, if anything.” The climate is hardly ever average so reading too much into this isn’t the right thing to do, says Keim.

“Yes, we had a very unusual June but we got into a normal pattern in July and now, in August, it’s drying up. It seems the pendulum has swung in the other direction.

“The weather across the United States has been in an odd configuration for much of the summer. The jet stream was displaced south over the Delta. This latest front that came through (in early August) is an example of that – it looked like a system you’d see in the winter. It was welcome, of course, because it kept temperatures down. But if that same thing had happened in, say, January, it would have produced a deep freeze in the South. It’s really strange to see a cold front of that substance make it this far south in the summer – and we’ve had three or four of those in the last couple of months.”

Over the harvest months the prediction is for an above normal tropical season, says Keim. “There’s a system in the Gulf now, Bonnie, that appears ready to hit land around the panhandle of Florida. It wouldn’t take a big shift for Bonnie to dump a lot of water around the Delta.”

On the upper end of the Delta, odd weather has also been in evidence. July temperatures in Missouri were the coolest in 37 years. This summer could set a record for coolest ever recorded.

Looking at the entire nation, Guinan says the eastern two-thirds have remained cooler than normal. The remaining western third has had warmer weather than usual.

"It's been a pattern that's established itself this summer,” Guinan says. “The heat waves we've had have been few and far between, and they've only lasted a few days."

In southeast Missouri, June temperatures were about 0.5 to 1.5 degrees below the norm.

"Preliminary temperature reports indicate this ranks as the eleventh coolest June-July period on record, and that goes back to 1895," Guinan says. "When you look at July alone, it's the ninth coolest on record."

Missouri rainfall for July averaged 5.75 inches, nearly 2 inches more than the 30-year average of 3.96 inches.

"Pretty much the entire state is looking nice and green throughout," Guinan says. "It's unusual to have this weather persist."